System and method for regulating pressure of pilot air to combustor of gas turbine

Abstract

A pilot air system for providing pilot air to a combustor of a gas turbine wherein the system includes: an inlet to receive a portion of compressed air discharged by a compressor of the gas turbine, wherein the portion of the compressed air is pilot air; a main passageway coupled to the inlet and providing a passage for the pilot air; an inline throttling valve coupled to the main passageway and metering a pressure of the compressed air in the main passageway; a pilot air compressor in series with the main passageway; a by-pass passageway for the pilot air and arranged in parallel to the main passageway and compressor, wherein the by-pass passageway receives pilot air from the main passageway downstream of the compressor and passes a portion of the compressed pilot air to the main passageway upstream of the compressor; a by-pass throttling valve inline with the by-pass passageway to meter pilot air flowing through said by-pass passageway, and the main passageway is connectable to the combustor.

1. A pilot air system for providing pilot air to a combustor of a gas turbine wherein the system comprises:
 an inlet to receive a portion of compressed air discharged by a compressor of the gas turbine, wherein the portion of the compressed air is pilot air; 
 a main passageway coupled to the inlet and providing a flow passage for the pilot air; 
 an inline throttling valve coupled to the main passageway and metering a pressure of the compressed air in the main passageway; 
 a pilot air compressor in series with the main passageway; 
 a by-pass passageway for the pilot air and arranged in parallel to the main passageway and pilot air compressor, wherein said by-pass passageway receives pilot air from the main passageway downstream of the pilot air compressor and passes a portion of the compressed pilot air to the main passageway upstream of the pilot air compressor; 
 a by-pass throttling valve inline with said by-pass passageway to meter pilot air flowing through said by-pass passageway; and 
 said main passageway having an outlet connectable to said combustor. 
 
   
   
     2. A pilot air system as in  claim 1  further comprising a heat exchanger in series with said main passageway downstream of the inlet and upstream of the pilot air compressor. 
   
   
     3. A pilot air system as in  claim 2  wherein said heat exchanger is an adjustable heat exchanger and further comprises a variable speed fan and a radiator in series with said main passageway. 
   
   
     4. A pilot air system as in  claim 2  further comprising a controller regulating a pressure of the pilot air at the outlet by adjusting the heat exchanger. 
   
   
     5. A pilot air system as in  claim 1  further comprising a moisture separator in series with said main passageway. 
   
   
     6. A pilot air system as in  claim 1  further comprising a butterfly valve in series with said main passageway. 
   
   
     7. A pilot air system as in  claim 1  wherein said inline throttling valve is a first and second throttling valve in a parallel arrangement. 
   
   
     8. A pilot air system as in  claim 1  wherein said outlet is connectable to a pilot air manifold of said combustor. 
   
   
     9. A pilot air system as in  claim 1  wherein said throttling valves adjust an increases in pilot air pressure such that a pressure of the pilot air at the outlet is in a range of 1.00 to 1.50 of the pilot air pressure at the inlet. 
   
   
     10. A pilot air system as in  claim 1  wherein said throttling valves adjust an increases in pilot air pressure such that a pressure of the pilot air at the outlet is in a range of 1.05 to 1.25 of the pilot air pressure at the inlet. 
   
   
     11. A pilot air system for providing pilot air to a combustor of a gas turbine wherein the system comprises:
 a main pilot air main passageway having an inlet adapted to receive compressed air discharged by a compressor of the gas turbine; 
 a pilot air compressor coupled to said main passageway to boost pilot air in said passageway; 
 a first throttling valve in said main passageway and inline with said compressor; 
 a by-pass passageway having an inlet joined to said main passageway downstream of the pilot air compressor and an outlet joined to said main passageway upstream of the compressor; 
 a by-pass throttling valve coupled to said by-pass passageway; and 
 an outlet connectable to the combustor of the gas turbine. 
 
   
   
     12. A pilot air system as in  claim 11  further comprising a heat exchanger coupled to said main passageway downstream of the inlet and upstream of the compressor. 
   
   
     13. A pilot air system as in  claim 12  wherein said heat exchanger further is an adjustable heat exchanger and further comprises a variable speed fan and a radiator inline with said main passageway. 
   
   
     14. A pilot air system as in  claim 12  further comprising a controller regulating a temperature of the pilot air by adjusting the heat exchanger. 
   
   
     15. A pilot air system as in  claim 11  further comprising a moisture separator in said main passageway. 
   
   
     16. A pilot air system as in  claim 11  further comprising a butterfly valve in said main passageway. 
   
   
     17. A pilot air system as in  claim 11  wherein said first and second throttling valves are in a parallel arrangement. 
   
   
     18. A pilot air system as in  claim 11  wherein said second pipe outlet is connectable to a pilot air manifold of said combustor. 
   
   
     19. A pilot air system as in  claim 11  wherein said throttling valves adjust an increases in pilot air pressure such that a pressure of the pilot air at the outlet is in a range of 1.00 to 1.50 of the pilot air pressure at the inlet. 
   
   
     20. A pilot air system as in  claim 11  wherein said throttling valves adjust an increases in pilot air pressure such that a pressure of the pilot air at the outlet is in a range of 1.05 to 1.25 of the pilot air pressure at the inlet. 
   
   
     21. A method for providing pilot air to a combustor of a gas turbine comprising:
 directing a portion of compressed air from a discharge of a compressor in the gas turbine to a pilot air main passageway, wherein said air in the main passageway is pilot air; 
 directing another portion of the compressor discharge air directly into the combustor; 
 boosting pressure of the pilot air with a pilot air compressor in the main passageway; 
 providing a by-pass passageway coupled to the main passageway both downstream and upstream of the pilot air compressor directing a portion of the compressed pilot air in the main passageway; and 
 regulating the pressure of the pilot air at the combustor by at least one throttling valve in the main passageway and a by-pass throttling valve in the by-pass passageway. 
 
   
   
     22. A method for providing pilot air as in  claim 21  further comprising:
 cooling the pilot air upstream of the pilot air compressor to a predetermined pilot air temperature. 
 
   
   
     23. A method for providing pilot air as in  claim 22  further comprising:
 selecting the predetermined pilot air temperature to achieve a desired pressure of the pilot air at the combustor. 
 
   
   
     24. A method for providing pilot air as in  claim 22  further comprising:
 selecting the predetermined pilot air temperature to achieve a desired pressure ratio the pilot air at the combustor to the compressed air at the compressor discharge.